Proteins analogous to actin, myosin, tropomyosin and troponin of striated muscle are also present in brain cells. The interaction of actin with myosin are regulated by several mechanisms. One of these mechanisms operate via the Ca2 ion-troponin-tropomyosin system and another by phosphorylation of light chains associated with the myosin. The objectives of this proposal are to study these regulatory systems as they apply to nervous tissue actin and myosin. Their interactions will be measured by MgATPase activity and by binding of 125I labelled tropomyosin and troponins to the system. Peptide mapping of the brain troponins will be compared with those from muscle. Phosphorylation of the brain myosin will be studied and the associated kinase and phosphatase identified. The effect of phosphorylation on ATPase activity will be evaluated. Bovine brain will be the source of the proteins.